In recent years, a semiconductor device such as a semiconductor module is widely used for a power conversion apparatus such as an inverter and a converter.
FIGS. 8A and 8B are configuration views illustrating a conventional semiconductor device 700. FIG. 8A is a sectional view of an essential part thereof. FIG. 8B is an enlarged view of the part B illustrated in FIG. 8A. In the semiconductor device 700, the back surface of a semiconductor chip 61 is joined to an insulating substrate 51 with a conductive pattern through joining material 66 such as solder. The front surface of the semiconductor chip 61 is joined to implant-pins 63 of a printed-circuit board 62 with implant-pins through joining material 67 such as solder. Electric wiring connected to the implant-pins 63 is formed onto the printed-circuit board 62 (see Patent Literature 1). In addition, the insulating substrate 51 with the conductive pattern can be called as a DCB (Direct Copper Bonding) substrate. The implant-pins 63, which are inserted to the printed-circuit board 62, also indicate conductive posts (pins) connected to the conductive pattern formed on the printed-circuit board 62.
The semiconductor chip 61 and the insulating substrate 51 with the conductive pattern are sealed by a mold resin 65 in the structure. The insulating substrate 51 with the conductive pattern includes an insulating substrate 52 such as ceramics, a conductive pattern 53 formed on the front surface 52a of the insulating substrate 52, and a rear heat-sink 54 formed on the back surface 52b. The rear heat-sink 54 is exposed from the mold resin 65, and the surface height thereof is the same level as that of the mold resin 65. Further, the conductive pattern 53 is formed by performing diffusion bonding 59 of a thick copper plate 53a with a thin copper film 53b. The thin copper film 53b, which is a thin copper foil on which a circuit pattern is formed, is attached on the front surface 52a of the insulating substrate 52. Furthermore, the rear heat-sink 54 is formed by performing the diffusion bonding 59 of a thick copper plate 54a with a thin copper film 54b. The thin copper film 54b is attached on the back surface 52b of the insulating substrate 52. The thicknesses of the thin copper films 53b and 54b are, for example, several hundred micrometers, and the thicknesses of the thick copper plates 53a and 54a are, for example, about 1 mm. Besides, reference numerals 64 in the figure show leading terminals.
The insulating substrate 52 constituting the insulating substrate 51 with the conductive pattern ensures the insulation between the semiconductor chip 61 and a heat dissipation fin that the rear heat-sink 54 contacts and has a function to transmit the heat generated in the semiconductor chip 61 to the heat dissipation fin. The heat generated in the semiconductor chip 61 will be conducted to the heat dissipation fin through the conductive pattern 53, the insulating substrate 52, the rear heat-sink 54, and a compound (not shown). Thus, this structure allows the heat to be radiated mainly in one direction from the backside of the semiconductor chip 61 and then results in single side cooling. The compound is used to lower the contact thermal resistance between the rear heat-sink 54 and the heat dissipation fin.
In this structure, the thick copper plates 53a and 54a are used for the conductive pattern 53 and the rear heat-sink 54, respectively. The heat diffuses into copper and then passes through ceramics that has lower conductivity. This is effective to reduce thermal resistance and increases thermal capacity. Thus this enables rapid temperature rising to be suppressed during overload operation.
Further, the package employed for the semiconductor device 700 sealed with the mold resin 65 is a full mold package, which has following characteristics in comparison with a gel filling package employed for an ordinary semiconductor module or the like.    (1) The use of high heat-resistant material such as an epoxy resin for the mold resin 65 allows a heat-resistant temperature to rise.    (2) Fixing the semiconductor chip 61 and the wiring with the mold resin 65 results in holding excellent properties against vibration.    (3) Simultaneous achievement of both molding an outer shape and filling the inside lowers cost.
FIG. 9 is a sectional view of an essential part of another conventional semiconductor device 800. The semiconductor device, which is a semiconductor module, includes a radiation base 71, an insulating substrate 72 with a conductive pattern, which is fixed on the radiation base 71, a semiconductor device 74 fixed on the conductive pattern 73 of the insulating substrate 72 with the conductive pattern and an external lead 75, and a mold resin 76 that seals those members. A groove 77 that surrounds the insulating substrate 72 with the conductive pattern is formed on the front surface of the periphery of the radiation base 71. The groove 77 prevents the mold resin 76 from delaminating (see Patent Literature 2).
Patent Literature 3 further provides as follows: A semiconductor device has a chip base, a semiconductor chip, and lead terminals stacked in this order on a heat-sink metal base. A case is attached to this structure, with a mold resin but inside the casing. Formed in the periphery of the chip base is a groove with a visor portion. The mold resin enters the groove to generate an anchoring effect, so that the mold resin is prevented from being delaminated from the chip base due to a heat cycle.
Patent Literature 4 further provides as follows: Related to a resin-mold semiconductor device wherein a semiconductor chip is soldered to a metal base, which is sealed with a mold resin, on the side surface of a metal base, a groove parallel to the surface bonded to an MOSFET chip of the metal provides highly-reliable semiconductor device excellent in environment-resistance, such as high-temperature and high-humidity.